Evidence indicates that the cause of the kill was low dissolved oxygen. Dissolved
oxygen levels naturally decrease at night as algae switch from producing oxygen
(photosynthesis) to consuming oxygen (respiration). Measurements of dissolved oxygen
levels in the area since the kill have shown very low levels. It is hypothesized
that a large school of menhaden moved into Bullbegger Creek to feed or avoid predators.
As oxygen levels naturally decreased after dark, the large amount of fish in the
relatively confined waters of Bullbegger Creek further reduced the oxygen concentrations
to lethal levels; resulting in the fish kill. Smaller fish kills due to low
dissolved oxygen are not uncommon during the summer, and are exacerbated by nutrient
enrichment and drought conditions.

As a precaution, water samples were collected and sent to seven laboratories for Pfiesteria
analysis. As of August 1, preliminary results have been received from five of the
laboratories. All results to date indicate that Pfiesteria was not involved
in the Bullbegger Creek kill

Maryland DNR and MDE are working with authorities in Virginia to monitor the situation
and collect additional information as needed.